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11 25 530 Removing and installing/replacing all pistons (N47)

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Special tools required: 

WARNING: Safety goggles must be worn when working on the gudgeon pin circlip.

Necessary preliminary work: 

IMPORTANT: If pistons, connecting rods and bearing shells are reused, they must be reinstalled in the same places.
Individual connecting rod replacement is not permitted; they are classified by weight class.
Connecting rods and connecting rod bearing caps are denoted with the same pairing letters; mixing them up will result in engine damage.
Piston and gudgeon pins are paired and must not be fitted individually or confused.
IMPORTANT: Do not release screw (1).
Oil spray nozzles (2) must not be maladjusted or bent.
A bent oil spray nozzle cannot be adjusted and must be replaced.
Fig 1: Oil Spray Nozzles Screw
G09920669Courtesy of BMW OF NORTH AMERICA, INC.
IMPORTANT: Position crankshaft vertically.
Proceed with care at the cylinder wall and oil spray nozzles Risk of damage  !
Fig 2: Crankshaft Position
G09944291Courtesy of BMW OF NORTH AMERICA, INC.

Undo the connecting rod bolt (1).

Remove connecting rod bearing caps (2) and set down in neat order.

Fig 3: Connecting Rod Bearing Caps And Bolt
G09920670Courtesy of BMW OF NORTH AMERICA, INC.

Screw special tool 11 8 860 in at large connecting rod eye.

Remove piston and connecting rod.

Installation note: 

Pay attention to the protective edge for the cylinder wall.

Fig 4: Special Tool (11 8 860)
G09920671Courtesy of BMW OF NORTH AMERICA, INC.

Position piston (1) with connecting rod on special tool 11 8 831 .

Fig 5: Positioning Piston With Connecting Rod On Special Tool (11 8 831)
G09920672Courtesy of BMW OF NORTH AMERICA, INC.
WARNING: Safety goggles  must be worn for the next operation.
WARNING: Safety goggles must be worn.

Lever out piston circlip (1) with special tool 11 5 464 in direction of arrow.

IMPORTANT: Piston and gudgeon pin are matched to each other.
They must not be mixed up.
Fig 6: Turning Piston Circlip With Special Tool (11 5 464)
G09920673Courtesy of BMW OF NORTH AMERICA, INC.

If necessary, replace CONNECTING ROD BEARING .

Installation note: 

It must be possible to press gudgeon pin (1) through the bush (small connecting rod eye) and must not display any significant play.

Fig 7: Pressing Gudgeon Pin
G09920674Courtesy of BMW OF NORTH AMERICA, INC.

Before installation, measure piston installation clearance. Measure piston diameter with micrometer at measuring point A from lower edge of piston and offset at 90° to the axis of the gudgeon pin.

Distance A,

REFER TO TECHNICAL DATA .

Fig 8: Measuring Piston Diameter Using Micrometer
G04739771Courtesy of BMW OF NORTH AMERICA, INC.

Adjust micrometer to cylinder bore of engine block. Set internal measuring device on micrometer to zero. Measure bottom, center and top of cylinder bore in direction of travel and direction of rotation.

Diameter of the cylinder bore,

TECHNICAL DATA .

Piston installation clearance,

TECHNICAL DATA .

Permitted total wear clearance,

TECHNICAL DATA .

Fig 9: Checking Cylinder Bore Diameter
G04739772Courtesy of BMW OF NORTH AMERICA, INC.
WARNING: Safety goggles  must be worn.

Fit gudgeon pin retaining ring (1) in connecting rod at the piston.

Fig 10: Installing Gudgeon Pin Retaining Ring In Connecting Rod
G09920677Courtesy of BMW OF NORTH AMERICA, INC.
IMPORTANT: Piston and gudgeon pin are matched to each other.
They must not be mixed up.
Install circlip so that opening is opposite recess.
Fig 11: Installing Circlip
G09920678Courtesy of BMW OF NORTH AMERICA, INC.

Align contact points of PISTON RINGS  (offset at approx. 120°, but do not arrange over gudgeon pin boss).

Lightly coat pistons and piston rings with oil.

Prepare piston with piston rings on special tool 11 8 140 .

Screw special tool 11 8 860 on at large connecting rod eye.

Fig 12: Aligning Piston Rings Contact Points
G09920679Courtesy of BMW OF NORTH AMERICA, INC.

Insert piston (1) with connecting rod in cylinder.

IMPORTANT: Risk of piston ring breakage.
Risk of damage to oil spray nozzle.
Only press pistons in with finger force - do not  knock in!
Fig 13: Installing Piston Using Special Tool (11 8 140)
G06852843Courtesy of BMW OF NORTH AMERICA, INC.

Install piston so that arrow points forward in direction of travel.

Bolt piston (1) with connecting rod to crankshaft.

The gasket thickness must be recalculated when repair work is carried out on the crankshaft drive or pistons.

Measuring the piston protrusion: 

Fit dial gauge with measuring fixture special tool 00 2 530 on cleaned engine block sealing surface and set to zero under preload.

Fig 14: Measuring Piston Protrusion
G06852847Courtesy of BMW OF NORTH AMERICA, INC.

Position piston at TDC.

Clean piston at measuring points (1 and 2).

Fit dial gauge at measuring point (1) on piston and determine highest point by rotating crankshaft.

Measure and note down piston protrusion at measuring points (1 and 2) on all pistons.

Determine THICKNESS OF CYLINDER HEAD GASKET .

Fig 15: Installing Dial Gauge On Piston
G06852848Courtesy of BMW OF NORTH AMERICA, INC.

Assemble engine.

Check engine function and check for leak tightness.

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